tools/pygrub: Make pygrub understand default entry in string format

Currently pygrub can only correctly parse grub2's default attribute when it is
specified as a number. If it is set to ${saved_entry} or ${next_entry} then
the first image (i.e. entry number 0) is selected. If any other value is
specified (typically this would be the string in menuentry) pygrub will crash.

This patch will allow pygrub to interpret default attribute if it is specified
as a string (note that in case of submenus only the leaf string will be
considered).

Also issue a warning if default is set to ${saved_entry} or ${next_entry}.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

tools/pygrub/src/GrubConf.py

@@ -231,7 +231,7 @@ class _GrubConfigFile(object):
         if val == "saved":
             self._default = 0
         else:
-            self._default = int(val)
+            self._default = val
 
         if self._default < 0:
             raise ValueError, "default must be positive number"
@@ -431,11 +431,11 @@ class Grub2ConfigFile(_GrubConfigFile):
                 
             if self.commands.has_key(com):
                 if self.commands[com] is not None:
-                    if arg.strip() == "${saved_entry}":
+                    arg_strip = arg.strip()
+                    if arg_strip == "${saved_entry}" or arg_strip == "${next_entry}":
+                        logging.warning("grub2's saved_entry/next_entry not supported")
                         arg = "0"
-                    elif arg.strip() == "${next_entry}":
-                        arg = "0"
-                    setattr(self, self.commands[com], arg.strip())
+                    setattr(self, self.commands[com], arg_strip)
                 else:
                     logging.info("Ignored directive %s" %(com,))
             elif com.startswith('set:'):

tools/pygrub/src/pygrub

@@ -450,9 +450,28 @@ class Grub:
     def run(self):
         timeout = int(self.cf.timeout)
 
-        self.selected_image = self.cf.default
+        if self.cf.default.isdigit():
+            self.selected_image = int(self.cf.default)
+        else:
+            # We don't fully support submenus. Look for the leaf value in
+            # "submenu0>submenu1>...>menuentry" and hope that it's unique.
+            title = self.cf.default
+            while 1:
+                try:
+                    title = re.search('(\S)>(\S.+$)',title).group(2)
+                except AttributeError:
+                    break
+
+            # Map string to index in images array
+            self.selected_image = 0
+            for i in range(len(self.cf.images)):
+                if self.cf.images[i].title == title:
+                    self.selected_image = i
+                    break
+
         # If the selected (default) image doesn't exist we select the first entry
         if self.selected_image > len(self.cf.images):
+            logging.warning("Default image not found")
             self.selected_image = 0
         self.isdone = False
         while not self.isdone: